A: Background + Plan

New updates on this page tell you more about the energy and carbon targets and separately go some way to defining a budget concept for this type of retrofit work.


There are some 7 million solid wall domestic properties in the UK, nearly all without insulation and representing part of one of the oldest and least efficient housing stocks in Europe (Boardman, B., et al, 2005). Solid wall insulation is considered costly and disruptive. Internally applied it consumes living space in dwellings that typically don't have a lot of space to start with. And yet these highly inefficient properties of low value and often in poor condition which are hard to heat and keep warm are surely likely to occupied in many cases by those least able to afford rising fuel prices. 

I'd really like to know whether it is possible to bring these homes to a reasonable standard. There are examples of it being done but publicised exemplar projects often have budgets for refurbishment twice the value of this property after refurbishment or have significant State regeneration subsidy, (I'm not going to back up this statement, but if you want the examples then let me know!) Neither answer the need to improve the household and environmental performance of homes in the private sector, privately or landlord owned.

This house when acquired had virtually no electricity, (3 working lights and no upstairs power), only limited gas, and a collapsed ground floor. Damp levels were very high. The roof and frontage of the house have structural problems masked by state funded cosmetic refurbishment in 2009.


What can reasonably be done to improve the energy efficiency of this dilapidated Manchester terraced house? What are the energy implications of the refurbishment process? How do we economically refurb low value properties to achieve greater energy efficiency without making them unaffordable? What are the trade off's along the way between energy, materials and budget? And any other stuff that comes to attention along the way....

The idea is to refurbish the house to achieve the best performance possible in relation to these  priorities:

  1. Increasing insulation
  2. Improving airtightness 
  3. Managing ventilation
  4. Limiting embodied energy in refurbishment

Focus on insulation and air tightness necessarily results in a related focus also on ventilation as both have a significant impact (see Section G). Air tightness is of particular interest in this refurbishment because it so often ignored when people talk about improving energy efficiency. Remember when everyone use to have foam round every doorway, (I know you're not that old)? These days people seem to go and on about loft insulation and forget or fail to realise that warm air will leak out through an old wooden loft hatch. Likewise cavity wall insulation is about as good at the number of leakage routes around openings for doors, windows, pipes etc that cold air will seep in through or warm air escape. Insulation measures are only maximised by combination with air tightness measures.

These priorities are limited by the constraint of a maximum resale value for this type of property and therefore a limited refurbishment budget. It is possible to define this in general terms:

  1.  The setting for the project is low value property in the private sector where “low value” might be defined as a market valuation below the national average for property of that type. 
  2. An appropriate perspective to define a retrofit budget might be defined as “an amount less than the equity in the property according to its post refurbishment market valuation”. The degree to which the retrofit cost is less than the equity might be considered the potential profit margin were the property to be resold.


I remember being asked by the head of my MSc course right in the middle of my thesis presentation "Sustainability? What does that mean? I don't know what it means" (Thompson, M., January 2009). So I spent ages defining it for my thesis and have tried to avoid using the term ever since. it's certainly a bit of a catch all, and hence this project being very specific. What we're after is low energy in build and in use. 

Some of this project is a bit cart before horse and this is reflected in the learnings in Section L of this website. I'm also wary of being prescriptive on targets although I recognise that saying I'm aiming for the 'best I can get' while pragmatic relative to a tight budget is at the same time perhaps a bit of a cop out. Each section of this website gives more detail on the work being done and the measurements where applicable but in brief summary the following areas are being targeted and measured (even if retrospectively in one or two cases):

  • U-values of individual elements of the envelope of the building before and after (walls. floor, ceiling, openings)
  • Air tightness of the envelope (before and after)
  • Space heat demand (before and after)
  • Carbon emissions (before and after)
  • Energy Performance Certificate rating (before and after)
  • Embodied energy of materials used and disposed of in the refurbishment process 

For this project 'before' means for a typical property (for which a nearby property is to be assessed) as the lower-energy-terraced-house was so dilapidated as to be virtually uninhabitable and therefore not a reasonable basis for assessment.

The house retrofitted with the range of measures described above might reduce annual energy demand by circa 62% from 29MWh to 11MWh, and consequently reduce carbon emissions by 57% from 9 tonnes to 4 tonnes. This would have the effect of improving the EPC rating from “F” to “C”, (energy model produced using Carbon Mixer 2).


The house was very dilapidated with collapsing floors, holes everywhere, damp, condemned wiring etc. This and the fact that it is empty provides an opportunity to refurbish with a blank(ish) canvas and without having to worry about owner occupation, which it has to be said would be a nightmare! There is a constraint though..., money! This type of house has a ceiling of about £130,000 re-sale value in a buoyant market, perhaps only £110,000 now, so the budget has to be kept tight. Nonetheless the house will have when complete (in addition to structural repairs and usual refurbishment renewal work including rewire and plumbing, kitchen, bathroom etc):

  • New highly insulated suspended timber ground floor
  • Solid wall insulation of exterior walls
  • New high quality timber double glazed windows
  • New insulated back (kitchen) external door
  • Super insulated loft space and hatch
  • Insulation of all pipework and ducting
  • Air tightness membrane/ taping throughout building envelope
  • Glazed ground floor internal doors to draw light into hallway
  • Glazing above first floor internal doorways to draw light into stairwell and landing
  • Unheated draught lobby to front door
  • Light pipe above landing/ stairwell
  • Demand controlled mechanical ventilation system
  • Etc....
Additionally there are some obvious things to try and get right, everything from trying to minimise the impact of materials used to making sure the heating and hot water controls don't require a Ph.D. level intellect to understand how to operate them.


I'm a recent graduate of an MSc in 'Architecture: Advanced Environment and Energy Studies' at the Centre for Alternative Technology in Wales. More about their courses can be found here http://www.cat.org.uk/ and http://gse.cat.org.uk/  .My background is in retail but my daughter thinks I'm a builder so that's qualification enough isn't it? I'm also a member of the sustainable building association AECB http://www.aecb.net .

Thanks for reading,

perma low energy homes